Drawing table

ABSTRACT

A drawing table comprising a cylindrical elevatory member urged to move upwardly by a gas spring means or other rod-like telescopic resilient means and slidably supported by an upstanding cylindrical support member supported in turn by a horizontal support base. The vertical position of a drawing board support frame mounted on the cylindrical elevatory member can be adjusted freely by moving the cylindrical elevatory member up and down along the cylindrical support member. The rod-like telescopic resilient means is detachably inserted at its lower end in a receiving portion formed in the horizontal support base and at its upper end in a receiving portion formed in a cap removably mounted on the upper end of the cylindrical elevatory member, and disposed such that is center vertical axis is in the same position as the center vertical axis of the cylindrical support member. By removing the cap from the upper end of the cylindrical elevatory member, it is possible to take out the rodlike telescopic resilient means freely from within the cylindrical elevatory member. There is provided a safety mechanism which ensures that the cap is removed from the upper end of the cylindrical elevatory member only when the rod-like telescopic resilient means is fully extended and disposed in its uppermost position.

United States Patent [191 Komura Nov. 18, 1975 DRAWING TABLE [75] Inventor: Seiichi Komura, Osaka, Japan [73] Assignee: Mutoh Industry Ltd., Tokyo, Japan [22] Filed: Nov. 20, 1973 [21] Appl. No.: 417,530

[30] Foreign Application Priority Data Nov. 28, 1972 Japan 47-136090[U] Nov. 28, 1972 Japan 47-136083[U] Nov. 28, 1972 Japan 47-136082[U] [52] US. Cl. 248/162; 108/2; 108/146 [51] Int. Cl. F16M 11/28; A47F 85/00 [58] Field of Search 108/2, 136, 146, 147; 248/162, 297/347, 345

[56] References Cited UNITED STATES PATENTS 1,999,844 4/1935 McElroy 248/162 UX 2,636,348 4/1953 Murray 108/147 X 3,444,830 5/1969 Doetsch 108/2 X 3,682,424 8/1972 Strumpell 248/162 lOb [57] ABSTRACT A drawing table comprising a cylindrical elevatory member urged to move upwardly by a gas spring means or other rod-like telescopic resilient means and slidably supported by an upstanding cylindrical support member supported in'turn by a horizontal support base. The vertical position of a drawing board support frame mounted on the cylindrical elevatory member can be adjusted freely by moving the cylindrical elevatory member up and down along the cylindrical support member. The rod-like telescopic resilient means is detachably inserted at its lower end in a receiving portion formed in the horizontal support base and at its upper end in a receiving portion formed in a cap removably mounted on the upper end of the cylindrical elevatory member, and disposed such that is center vertical axis is in the same position as the center vertical axis of the cylindrical support member. By removing the cap from the upper end of the cylindrical elevatory member, it is possible to take out the rod-like telescopic resilient means freely from within the cylindrical elevatory member. There is provided a safety mechanism which ensures that the cap is removed from the upper end of the cylindrical elevatory member only when the rod-like telescopic resilient means is fully extended and disposed in its uppermost position.

4 Claims, 12 Drawing Figures U.S..Patent Nov. 18, 1975 Sheet 1 of7 3,920,209

l4 7 I715 53 I50 |q g 726 42s US. Patent Nov. 18,1975 Sheet20f7 3,920,209

US. Patent Nov. 18,1975 Sheet30f7 3,920,209

US. Patent Nov. 18, 1975 Sheet4 0f7 3,920,209

US. Patent Nov. 18,1975 Sheet5of7 3,920,209

US. Patent Nov. 18,1975 Sheet6of7 3,920,209

L. is ,4 v a US. Patent Nov. 18, 1975 Sheet 7 of7 3,920,209

FIG. /0

DRAWING TABLE BACKGROUND OF THE INVENTION This invention relates to drawing tables, and more particularly it is concerned with a drawing table comprising a cylindrical elevatory member slidably supported by an upstanding cylindrical support member supported in turn by a horizontal support base and adapted to be urged to move upwardly by the biasing force of a rod-like telescopic resilient means whereby the vertical position of a drawing board support frame mounted on the cylindrical elevatory member can be freely adjusted.

Drawing tables of the prior art which are capable of adjusting their vertical position have generally been constructed such that the leg supporting the drawing table consists of two sections, one telescopically inserted in the other, which can be extended or contracted and held in a desired position by a screw. To move from one vertical position to another requires loosening the screw, telescopically extending or contracting the leg, and tightening thescrew when the table has been moved to a desired position. This operation is time consuming and troublesome.

SUMMARY OF THE INVENTION A principal object of the invention is to provide a drawing table comprising a cylindrical elevatory member slidably supported by an upstanding cylindrical support member supported in turn by a horizontal support base, the cylindrical elevatory member having removably mounted on its upper end a cap formed therein with a receiving portion and also having mounted therein a rod-like telescopic resilient means inserted at its upper end in the receiving portion formed in the cap and at its lower end in a receiving portion formed in the horizontal support base, so that the cylindrical elevatory member can be urged to moved upwardly by the biasing force of the rod-like telescopic resilient means which can be replaced by a new one with ease by removing the cap from the upper end of the cylindrical elevatory member.

Another object of the invention is to provide a drawing table in which the rod-like telescopic resilient means is a gas spring means capable of urging the cylindrical elevatory member to move upwardly by a substantially constant biasing force by its own inherent characteristic regardless of the position of the cylindrical elevatory member.

Another object of the invention is to provide a drawing table in which the imaginary line connecting the center of the receiving portion formed in the horizontal support base with the center of the receiving protion formed in the cap coincides in position with the center axis of the cylindrical support member and the cylindrical elevatory member and the receiving portion formed in the cap is disposed in a recess defined by a downwardly diverging wall surface portion of the underside of the cap, so that the upper end of the rod-like telescopic resilient means can be brought into engagement with a major diameter wall surface portion disposed above the downwardly diverging wall surface by threadably mounting the cap on the upper end of the cylindrical elevatory member, and the rod-like telescopic resilient measns can be mounted in a position in which it is disposed in the center of the cylindrical support member and the cylindrical elevatory member.

Another object of the invention is to provide a drawing table in which the cap can be removably mounted on the upper end of the cylindrical elevatory member by bringing the threaded portion of the cap into engagement with the threaded portion at the upper end of the cylindrical elevatory member, and in which a safety mechanism is provided, the safety mechanism comprising a transverse hole formed in the cap for inserting therein a driver to turn the cap, the transverse hole having disposed therein a member adapted to prevent the introduction of the driver therein so as to prevent the insertion of the driver therein when the upper end of the rod-like telescopic resilient means is resiliently in engagement with the cap, the member for preventing the insertion of the driver in the transverse hole being removed from the transverse hole so as to permit the insertion of the driver in the transverse hole when the rod-like telescopic resilient means is fully extended and its upper and is not resiliently in engagement with the cap whereby the cap can be removed from the upper end of the cylindrical elevatory member.

According to the invention, there is provided a drawing table comprising a rod-like telescopic resilient 'means, a horizontal support base formed therein with a receiving portion for removably mounting therein a lower end of the rod-like telescopic resilient means, a cylindrical support member disposed upright and fixed at a lower end to the horizontal support base, a cylindrical elevatory member slidably supported in the cylindrical support member and having the rod-like telescopic resilient means disposed therein, and a cap removably mounted on an upper end of the cylindrical elevatory member and formed on its underside with a receiving portion for removably receiving therein an upper end of the rod-like telescopic resilient means, the cap being mounted on the upper end of the cylindrical elevatory member with the lower end of the rod-like telescopic resilient means being inserted in the receiving portion formed in the horizontal support base and the upper and thereof engaging in the receiving portion formed in the cap, whereby the cylindrical elevatory member can be urged to move upwardly by the biasing force of the rod-like telescopic resilient means.

According to the invention, there is also provided a drawing table comprising a safety mechanism in which a hole is formed in the cap for inserting therein a tool for turning the cap, and a member for preventing the insertion of such tool in the hole is disposed in the hole when the upper end of the rod-like telescopic resilient means is in engagement with the underside of the cap so as to keep the cap from being turned by the tool, whereby the cap can be removed from the upper end of the cylindrical member only when the rod-like telescopic resilient means is fully extended and disposed in its uppermost position.

Additional and other objects and features of the invention will become evident from the description set forth hereinafter when considered in conjunction with the drawings.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 is a front view of the drawing table according to the invention comprising one embodiment of the invention and showing the essential portions in section;

FIG. 2 is a front view, with certain parts being shown in section, of the drawing table shown in FIG. 1 in which the cylindrical elevatory member is in its uppermost position;

FIG. 3 is a fragmentary front view, on an enlarged scale of one end portion of the upper portion of the drawing table shown in FIG. 1, with certain parts being shown in section;

FIG. 4 is a perspective view of the cap;

FIG. 5 is a front view of the gas spring; 7

FIG. 6 is a sectionalview taken along the line A-A of FIG. I; I

FIG 7 is a front view, on an enlargedtscale, of the upper portion of the drawing table, with certain parts being shown in section;

FIG.8,is a sectional view taken along the line BB of FIG;.7;

FIG. 9 is a sectional view taken along the line B-'B of FIG. 7 andshowing the rotary pipe after being angularly rotated;

FIG. 10 is a sectional view taken along the line C.--C of FIG. 7;

FIG. 11 is a perspective view of the stopper plug; and 7:

FIG. 12 is a sectional view taken along the line D-D of H017.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, there is shown a drawing table generally designatedZ comprising a horizontal support base 1 including two horizontal bars 1c (only one is shown) disposed between an upper plate la and a lower plate lb and fixed thereto by bolts 3 and nuts/MA cylindrical support member 5 is secured at its lower end to the upper plate 1a and disposed upright on the support base. The cylindrical support member, 5 is formed at the upper endof its outer peripheral surface with a threaded portion 5a which is in threadable: engagement with a threaded portion of an annular member 7 secured to the upper end of the inner peripheral surface of an outer cylindrical member 6.,

Disposed within the cylindrical support member 5 is a cylindrical elevatory member 8 including an outer peripheral surface slidable positioned against a plurality of bushes 9 projecting inwardly from the inner, peripheral surface of the annular member 7 (See FIG. 6) and the upper and lower end portions of the inner. peripheral surface of brake cylinder 10. Fitted in the cylindri cal support member 5 is a support cylinder 11 positioned'at its lower end against the upper'plate 1a of the support base 1 and having disposed atits upper end an annular stopperlZ formed with an inclined upper end surface. The brake cylinder 10 is formed with an inclinded upper end surface 100 which is inengagement with a complementary inclined end'surface formed in the annular member 7 and with an inclined lower end surface 10b which is in engagement with the complementaryyinclined upper end surface formed in the stop per 12.

A stop ring 57 is mounted at the lower end of the cylindrical elevatory member 8 for sliding motion along the inner peripheral surface of the support cylinder 1 l. The brake cylinder 10 is constructed such that it has a large thickness at the upper and lower'end portions but i has a smallthickness in the intermediate portion, so

that it can bend in the intermediate portion. A plurality of handles 13 project outwardly from the outercylindrical member 6 at right angles thereto and are disposed .in positionsdiametrically opposite to each other. An internally threaded tubular member14 is secured to the upper end of the inner peripheral surface of the cylindrical elevatory member 8. 15 is a mounting block formed therein with a tubular portion 15a rotatably fit ted over. the upper end portion of the outer peripheral surface of the cylindrical elevatory member 8 and formed at the upper end of its inner peripheral surface with anvinwardly oriented projection.l6,- see FIG.,3.Q The inwardly oriented projection 16 is positioned at its lower end against the upper end surface of the internally threaded tube 14. I

17 is a caop formed on its underside with a columnar wall surface portion 17b disposed in the center top of the underside of the cap, a downwardly diverging wall, I

surface portion 17a defining an outwardly diverging re-v cess; and a major diameter wall surface portion 17c interposed between the columnar wall surface portion 17b and the upper end of the outwardly diverging wall surface portion 17a as shown in FIG. 3 and FIG. 4, with belowthe minor diameter flange 17e. .if the. threaded portion 17fon the outer peripheral surface of the cap 17 isbrought into threadable engagement withthe internally threaded tubular member l4,-then the lower 7' surface of the minor diameter flange 17a is positioned against the upper end of the internally threaded tubular member 14, the outer peripheral surface, of the minor diameter flange 17e ispositioned against the inner peripheral surface. of the inwardly oriented projection 16; and the lower surface of the major diameter flange 17d is positioned against the upper surface of the inwardly oriented projection 16. Thus the. inwardly directed projection 16 can move along the outer peripheral surface of the minor diameter flange 172 The center of the co-n lumnar wall surface portion 17b is disposed in the same position as the centerof the cylindrical elevatory mem ber 8.

within the cylindrical elevatory member'8 and'includes a piston rod 18a loosely received at its lower end por tion in an opening 19 formed in the upper plate la of the horizontal support base 1 and detachably fitted in a recess 20 formed in the lower plate lb thereof as shown in FIG. 1. The recess 20 is formed such that it is disposed in the center of the cylindrical elevatory member I 8; Detailed description .of the gas spring means 18 shall be omitted because it is described in detail in U.S.. Pat. No. 3,207,498. The gas spring means 18 also includes a cylinder 18b formed at its upper end with a minor diameter portion substantially of the same length and diameter as the major diameter wall surface portion 17c disposed below the columnar wall surface portion.

1711 on the underside of the capl7.

. 21is a pin formed in the center of its outer peripheral surface with a recess 21a and slidably disposed in the recess defined by the columnarqwall surface portion 17b. 22 .is a cap screw threadably received 'in a' threaded opening formed in the side wall of the cap 17 and extending through the recess defined by the. columnar wall surface portion 17b so thatits forward end is I disposed in the recess 21a formed in the pin 21. 23 is a transverse hole extending transversely through the upper portion of the side wall of the cap 17 for inserting I therein a driver and having a central portion maintained in communication with the upper end of therecess defined by the columnar wall surface portion'l7b'.

A gas spring means 18 shown in FIG. 5 is mounted 24 is a fixing threaded rod (See FIG. 1) threadably received in a threaded opening formed in the tubular portion a of the mounting block 15 and disposed at right angles thereto. The threaded rod 24 has a forward end which is positioned against the side of the cylindrical elevatory member 8 and a rear end which has a handle 25 secured thereto. As shown in FIG. 1 and FIG. 7, a brake pipe 26 disposed horizontally is mounted on the mounting block 15 by a plurality of U,-bolts.27 and receives therein a rotary pipe 28 for rotation. A stopper ring 29 mounted on one portion of the rotary pipe 28 (See FIG. 7) has an inclined end surface which is positioned against one complementary inclined end surface 26a of the brake pipe 26. An annular pressor member 30 is slidably fitter over the other portion of the rotary pipe 28 and has an inclined end surface which is positioned against the other complementary inclined end surface 26a of the brake pipe 26. 31 and 32 are eccentric cams rotably supported by the rotary pipe 28 through shafts 33 and 34 respectively and connected to an operation lever (not shown). By pivotally moving the operation lever, it is possible to rotate the eccentric cams 31 and 32 simultaneously. The surfaces of cams 31 and 32 are positioned against an end surface of a tubular member 35 which is threadably connected to the pressor member 30 and slidable fitted over the rotary pipe 28.

As shown in FIG. 8 and FIG. 9, the brake pipe 26 is formed in its middle portion with an opening 36 through which extends a support shaft 37 projecting from the mounting block 15. The rotary pipe 28 is formed at its middle portion with a slot 38 extending for a circumferential extent on the order of 180. The support shaft 37 extends through the circumferential slot 38 so that the rotary shaft 28 can be angularly rotated through substantially l80. A torsion bar 39 is mounted within the rotary pipe 28. 40 is a columnar block slidably fitter within the rotary pipe 28 and formed in the center portion with a radial bore 41 extending at right angles to the longitudinal axis of the columnar block 40 and loosely receiving therein the forward end of the support shaft 37 which does not reach the center of the bore 41. A longitudinally extending slit 41a if formed in the columnar block 40 and disposed along the center axis thereof for receiving therein the central portion of the torsion bar 39.

42 and 42a are stopper plugs each comprisinga minor diameter portion 43 and a major diameter portion 44, as best seen in FIG. 11. The minor diameter portion 43 has an outer diameter which is substantially the same as the inner diameter of the rotary pipe 28, so that the stopper plugs 42 and 42a can be fitted in the rotary pipe 28. The stopper plugs 42 and 42a are identical with each other in construction, so that the plug 42 only will be described. 45 is a support bore formed in the plug 42 and opening in a space defined by the minor diameter portion 43. The support bore 45 is defined by a pairof regulating surfaces 45a and 45b and another pair of regulating surfaces 450 and 45d and formed such that the torsion bar 39 can be disposed therein with its opposite sides in engagement with one pair of regulating surfaces 45a and 45b as shown in FIG. 10 or with the other pair of regulating surfaces 450 and 45d.

46 is a notch formed on the outer circumferential surface of the minor diameter portion 43 and disposed on an extension of the regulating surfaces 45a and 45b, and 46a is another notch formed on the outer circumferential surface of the minor diameter portion 43 and disposed in a position diametrically opposite to that of the notch 46. The notches 46 and 46a are in communication-with a circumferential groove 47 formed in the minor diameter portion 43. 48 designates a plurality of stopper notches formed in the minor diameter portion 43 tobe equidistantly spaced apart from one another and disposed on aside wall of the circumferential groove 47 opposite to the side wall thereof on which the notches 46 and 46a are formed. The stopper notches 48 are also in communication with the circumferential groove 47.

49 and 50 are cap screws inserted in the rotary pipe 28 at one end portion thereof in positions diametrically opposite to each other. The cap screws 49 and 50 are positioned such that, as shown in FIG. 10, the line connecting the two cap screws is not in alignment with either of the two sides 390 or 39b of the torsion bar 39 but forms an angle therewith such that the torsion bar 39 is displaced counter clockwise with respect to the cap screws 49 and 50. 51 designates holes formed in the major diameter portion 44 of the stopper plug 42 I for selectively receiving therein a driver.

As shown in FIG. 12, a cutout portion 52 is formed in a portion of the rotary pipe 28 which is disposed near each end thereof. A square tubular member 53 of a drawing board support frame is fitted in each cutout portion 52 and disposed at right angles to the longitudinal axis of the rotary pipe 28. Lower opposite side surfaces 53a and 53b of each member 53 of the drawing board support frame are positioned against surfaces 52a and 52b respectively and a plate 54 secured to the underside of each member 53 is positioned against surfaces 52c and 52d of the cutout portion 52, so that the drawing board support frame is immovably supported in the cutout portions 52. 55 is a keep metal fixture including a curved portion 55a fitted over the rotary pipe 28 and horizontal portions 550 and 55d positioned against the plate 54 of each member 28. The keep metal fixture 55 is secured to the plate 54 by screws 56 and 57, so that the drawing board support frame can be firmly secured to the rotary pipe 28.

In operation, the cap 17 is removed from the upper end of the cylindrical elevatory member 8 and the lower end of the piston rod 18a of the gas spring means 18 is inserted in the recess 20 formed in the horizontal support base 1. Then, the cap 17 is replaced on the upper end of the cylindrical elevatory member 8. In this process, the upper end of the cylinder 18b of the gas spring means 18 is moved along the downwardly diverging wall surface portion 17a of the cap 17 into the top portion of the recess defined by the downwardly diverging wall surface portion 17a and brought into engagement with two major diameter portion 17c contiguous with the columnar wall surface portion 17b. If the cap 17 is turned and threadably fitted in the internally threaded tube 14 until the lower surface of the minor diameter flange 17e is brought into engagement with the upper end surface of the internally threaded tube 14, then the upper end surface of the cylinder 18b moves the pin 21 upwardly and comes into engagement with the shoulder 17g between the columnar wall surface portion 17b and the downwardly diverging wall surface portion 17a, so that the gas spring means 18 is held in position in the center of the cylindrical elevatory member 8 by being receiving at its lower end in the recess 20 in the horizontal support base 1 and by engagement with the major diameter portion 17c contigu- 7 ous with the columnar wall surface portion 17b of the cap 17.

If the drawing board support frame 53 is moved shows the cylindrical elevatory member 8 at its lower-' most position. The handles 13 are turned horizontally in a predetermined direction to turn the outer cylindricalmember6 when the cylindrical elevatory member is moved to a desired vertical position. This causes the outer cylindrical member 6 to move downwardly along the threaded portion a, so that the inclined end surface of the annular member 7 presses tightly against the complementary inclined end surface a of the brake cylinder 10 so as to bend the small thickness Portion of the brake cylinder 10. The inner peripheral surface of the bent brake cylinder 10 is brought into pressing engagement with the outer peripheral surface of the cylindrical elevatory member 8., with the result that the brake is applied to the cylindrical elevatory member 8. Thus the cylindrical elevatory member 8 can be held in position inthe desired vertical position in the cylindristill maintained under the influence of the upwardly biasingforce of the gas spring means 18.

By turning the tubular portiontlSa of the mounting 1 block 15 about the cylindrical elevatory member 8, it is possible to move the rotary pipe 28 in any direction as desired which is parallel to the horizontal. If the handle is turned to bring the threaded fixing rod 24 into pressing engagement with the outer peripheral surface of the cylindrical elevatory member 8, the mounting block 15 can be firmly fixed to the cylindrical elevatory member 8.' v

The old gas spring means 18 arranged in the cylindrical elevatory member 8 can be replaced by a new one as follows: If the cap 17 is turned and removed from the cylindrical elevatory member 8 when the latter is fixed in any lower position, the cylinder 18b will be suddenly upwardly by the gas pressure therein. This situation is very dangerous. According to the. invention, there is cal support member 6 while the elevatory member 8 is the major diameter wall surface portion '1 7c and the columnar wall surface portion i7b of the cap l7, with the result that the pin 21 moves downwardly relative to the columnar wall surface portion 17b and the upper end surface of the recess 21a therein abuts against the cap screw 22. Thus the pin 21 is' locked thecap screw 22. If the pin 21. movesdownwardlyrelative to the columnar wall surface' portion 1712 until the pin 21 is locked by the'cap screw'22,,then the upper end of'the pin 21 is removed from within the transverse hole 23' and is not present in the transverse hole 23 any longen At this time, if the driver 58 or a rod is inserted and v moved in the transverse hole 23 after the brake .is applied to the cylindrical elevatory member 8 as aforementioned to render the same immovable, it is possible i to turn the cap 17 and remove the same from the upper end of the cylindrical elevatory member 8 so as .to re place, the gas spring means lfi by anew onejSince the.

gas spring means 18 is in the fully extended state and no upwardly directed biasing force of the spring means is exerted on the cap 17, there is no danger-of the cylinder 18b suddenly moving upwardly even if the cap i7 is removed from the upper end of the cylindrical eieva-- tory'member 8. I

If the handles 13 are moved horizontally in the opposite direction to remove the braking force exertedon the; cylindrical elevatory member 3 when the latter is held in the lowermost position, then the cylindrical elevatory member 8 is suddenly moved upwardly by the biasing force of the gas spring means 18in case the downwardly directed load applied to the cylindrical elevatory member 8 is small, as when no drawing apparatus is mounted on the drawing board support frame I 53. When the cylindrical elevatory member 3 reaches its uppermost position, the stopper ring 57 strikes against the underside of the stopper l2-(See FIG. 2). The stopper 12 is moved upwardly by the impact of cola pressing engagement with the inclined lower end surp'rovided a safety mechanism wherein the upper end of the cylinder 18b moves the pin 21 upwardly and the upper end of the pin 21 is disposed midway in the transverse hole 23 to block it so as to prevent insertion of a driver 58 in the transverse hole, when the gas cylinder means 18 urges the cylinder 18b to move upwardly by its biasing force. if it is not possible to insert the driver 58 deep in thetransverse hole 23','it is not possible to I turn the cap 17 because the lever action of the driver 58 is not obtainable. Thus the safety mechanism functions such that it is not possible to remove the cap 17 when the gas spring means 18 is in its contracted position.

If the braking force exerted on the cylindrical elevatory member 8 is removed to permit the cylinder 18b of the gas spring means 18 to move to its uppermost posi.

face, of the annular member 7,' so that the small thickness portion of the brake cylinder Ed is bent and brought into pressing engagement withthe outer peripheral surface of the cylindrical elevatory member 8. In this way, the cylindricalelevatory member 8 is instantaneously fixed to the cylindrical support member 5 as soon as the stopper ring 57 strikes against the stopper 12, thereby relieving the shock which might otherwise be felt when the cylindrical elevatory memberfl stopsat its uppermost position. The invention has been described as using gas spring means 18 for urging'the cylindrical elevatory member 8 to move upwardly by its may be employed. I

The manner in which the torsion bar 39 is securedat:

its opposite ends to the opposite ends'of the rotary pipe 28 will be described with reference to FIG. 10 and FIG.

One end portion of the torsion bar 39 is inserted into the support bore formed in the stoppenplug 42, and

the'opposite sides of the torsion bar 39 are brought into engagement with the regulating surfaces 45a and 45b of the support bore 45. Then the stopper plug 42 is turned 9 counter clockwise in FIG. 10 against the resilient force of the torsion bar 39 to bring the notches 46 and 46a into alignment with the cap screws 49 and 50 respectively. Thereafter the forward end portion of the stopper plug 42 is forced into the bore of'the rotary pipe 28 to bring the cap screws 49 and 50 into engagement in the circumferential groove 47.,lf the force exerted on the stopper plug 42 is released at-this time, then the stopper plug 42 is slightly moved clockwise in FIG. 10 by the resilient force of the torsion bar 39 into a position in which the cutouts 46 and 46a are out of alignment with the cap screws 49 andSO, respectively. If one tries to pull the stopper plug 42 in a direction where it is removed from the rotary pipe 28, the stopper plug 42 cannot be dislodged from the rotary pipe 28 because the cap screws 49 and 50 abut against the walls of the circumferential groove 47 and merely bend, thereby holding the stopper plug 42 in place over the rotary pipe 28.

Then, the stopper plug 42 is rotated clockwise in FIG. 10 against the resilient force of the torsion bar 39 to bring a desired pair of stopper notches 48 into alignment with the cap screws 49 and 50. Thereafter, the stopper plug 42 is inserted deeper into the bore of the rotary pipe 28. Rotation of the stopper plug 42 clock-.

wise about the rotary pipe 28 in FIG. 10 brings the opposite sides of the torsion bar 39 into engagement with the regulating surfaces 45c and 45d respectively. If a pair of stopper notches 48 disposed in a counter clockwise sense in FIG. 10 with respect to the previous pair is selected and the aforementioned operation is repeated, it is possible to increase the resilient force of the torsion bar 39 which acts counter clockwise on the rotary pipe 28 in FIG. 10. Thus, if pressure is applied to the drawing board secured to the drawing board support frame to move the same from its normal inclined position to a horizontal position so as to thereby rotate the rotary pipe clockwise in FIG. 10, then the resilient force of the torsion bar 39 directed counter clockwise in FIG. 10 acts on the rotary pipe 28.

If it is desired to remove the stopper plug 42 from the rotary pipe 28 and release it from the torsion bar 39, the stopper plug 42 is pulled to remove the capscrew 49 and 50 from engagement in the selected pairs of stopper notches 48 and bring the same into engagement in the circumferential groove 47. Then the stopper plug 42 is rotated counter clockwise in FIG. 10 to bring the notches 46 and 46a into alignment with the cap screws 49 and 50 respectively. If the stopper plug 42 is pulled away from the rotary pipe 28 at this time, it is possible to dislodge the stopper plug 42 from the rotary pipe 28. The stopper plug 42a can be mounted on the other end of the rotary pipe 28 and moved in the same manner as described with reference to the stopper plug 42.

Let us assume that the drawing board supportframe or the drawing board supported thereon is normally inclined at an angle of 45 with respect to the cylindrical elevatory member 8, and that the torsion bar 39 is set such that the resilient force thereof does not act on the rotary pipe 28 or acts clockwise in FIG. 8 thereon when the drawing board support is in the normal position.

If a drawing apparatus or a coordinate analyzer is mounted on the drawing board when the latter is in its normal position, then a force tending to urge the drawing board to move into a position in which it is parallel with the horizontal is exerted on the drawing board by the drawing apparatus. Thus a force urging the rotary 10 pipe 28 to rotate counter clockwise in FIG. 8 acts on the rotary pipe 23 which is connected to the drawing board through the drawing board support frame. If the rotary pipe 28 is rotated in the direction of an arrow in FIG. 8 or FIG.-9 by this force then the torsion bar 39 secured to the opposite ends of the rotary pipe 28 also rotates in the direction of the arrow E. As a result, the

columnar block 40 connected to the torsion bar 39 also rotates in the direction of the arrow E about the support shaft 37 by virtue of the play between the support shaft 37 and the radial bore ,41, and the outer peripheral surface of the columnar block 40 is brought into pressing engagement with the inner peripheral surface of the rotary pipe. If a force is exerted on the rotary pipe 28 to further rotate the same in the direction of the arrow E or counter clockwise in FIG. 8, the rotary pipe 28 must rotate against the frictional force working between the inner peripheral surface of the rotary pipe 28 and the outer peripheral surface of the columnar block 40 and the resilient force of the torsion bar 39. Thus the greater the amount of angular rotation of the rotary pipe 28 in the direction of the arrow E, the greater is the resistance offered to its rotation. It will be seen that there is no danger of the drawing board support frame suddenly moving from its normal position even if the drawing apparatus is mounted thereon.

When one end 38a of the circumferential slot 38 of the rotary pipe 28 rotating in the direction of the arrow E is brought into engagement with the support shaft 37, the drawing board support frame or the drawing board supported thereon is disposed in a position in which it is parallel to the horizontal. If the lever (not shown) is moved to move the cams 31 and 32 (See FIG. 7) so as to bring their lobes into engagement with the end surface of thetubular member 35 after the rotary pipe 28 is set at a desired angular position, then the tubular member 35 and the pressor member 30 are pushed and moved in the direction of an arrow F by the lobes of the cams 31 and 32. As a result the inclined end surface of the pressor member 30 is brought into pressing engagement with one complementary inclined end surface 26a of the brake pipe 26,.and other inclined end surface 26a of the brake pipe 26 is brought into pressing engagement with the complementary inclined end surface of the stopper ring 29, so that the brake pipe 26 is compressed and its small thickness portion is bent toward the rotary pipe 28 and the inner peripheral surface of the brake pipe 26 is brought into pressing engagement with the outer peripheral surface of the rotary pipe 28. Thus the rotary pipe 28 is held in place in the desired angular position by the braking force of the brake pipe 26.

The drawing table according to the invention is constructed and operates as aforementioned. The gas spring means or other rod-like telescopic resilient means arranged in the cylindrical elevatory member can be readily replaced by a new one by merely removing'the cap detachably mounted on the upper end of the cylindrical elevatory member. The rod-like telescopic resilient means can be mounted in the cylindrical elevatory member by arranging the same therein and mounting the cap on the upper end of the cylindrical elevatory member. Moreover, the rod-like telescopic resilient means can be positioned in the center of the cylindrical elevatory member.

In addition, there is provided in the cap a safety mechanism which keeps the cap from being removed from the upper end of the cylindrical elevatory member o 11 7 when the rod-like telescopic resilient means is in a com tracted position, thereby eliminating the danger of the rod-like telescopic resilient means suddenly jumping disposed upright and fixed at a lower end thereof to said horizontal support base, a cylindrical elevatory member slidably supported in said cylindrical support member, and a cap removably mounted on an, upper end of said cylindrical elevatory member and formed at its underside with a receiving portion means for slid ably removably receiving and supporting therein an upper end of said rod-like telescopic resilient means, said rod-like telescopic resilient means being fitted in, said cylindrical elevatory member and slidably removably received at its lower end in said recess means formed in said horizontal support base and slidablydetachably received and supported at its upper end in said receiving portion means of said cap, said cap being mounted at the uppermost end of said cylindrical elevatory member, whereby the cylindrical elevatory memberca'n be urged to move upwardly by the biasing force of the rodlike telescopic resilient means.

2. A drawing table according to claim 1 wherein said: rod-like telescopic resilient means is a gas spring 7 means.

3. A drawing table according to claim 1 wherein said recess means formed in said horizontal support base is disposed in the center of said cylindrical elevatory member, and said receiving portion means formed in the cap is a recess defined by a downwardly diverging wall surface portion of the underside of the cap and adapted to receive therein the upper end of the rod-like telescopic resilient means.

4. A drawing table according to claim 1 further com-' I prising a, safety mechanism comprising a hole formed in the cap for inserting therein a tool for turning the cap,

and a member for preventing the insertion of such tool a in said hole disposed in said hole when the upper end of the rod-like telescopic resilient means is in engagement,

with the underside of the cap so as to keep the cap from beingturned by the tool, whereby the cap can be removed from the upper end of the cylindrical elevatoryl 

1. A drawing table comprising a self-containing rod-like telescopic resilient means, a horizontal support base formed therein with a recess means for slidably removably receiving a lower end of said rod-like telescopic resilient means, a cylindrical support member disposed upright and fixed at a lower end thereof to said horizontal support base, a cylindrical elevatory member slidably supported in said cylindrical support member, and a cap removably mounted on an upper end of said cylindrical elevatory member and formed at its underside with a receiving portion means for slidably removably receiving and supporting therein an upper end of said rod-like telescopic resilient means, said rod-like telescopic resilient means being fitted in said cylindrical elevatory member and slidably removably received at its lower end in said recess means formed in said horizontal support base and slidably detachably received and supported at its upper end in said receiving portion means of said cap, said cap being mounted at the uppermost end of said cylindrical elevatory member, whereby the cylindrical elevatory member can be urged to move upwardly by the biasing force of the rodlike telescopic resilient means.
 2. A drawing table according to claim 1 wherein said rod-like telescopic resilient means is a gas spring means.
 3. A drawing table according to claim 1 wherein said recess means formed in said horizontal support base is disposed in the center of said cylindrical elevatory member, and said receiving portion means formed in the cap is a recess defined by a downwardly diverging wall surface portion of the underside of the cap and adapted to receive therein the upper end of the rod-like telescopic resilient means.
 4. A drawing table according to claim 1 further comprising a safety mechanism comprising a hole formed in the cap for inserting therein a tool for turning the cap, and a member for preventing the insertion of such tool in said hole disposed in said hole when the upper end of the rod-like telescopic resilient means is in engagement with the underside of the cap so as to keep the cap from being turned by the tool, whereby the cap can be Removed from the upper end of the cylindrical elevatory member only when the rod-like telescopic resilient means is fully extended and disposed in its uppermost position. 